The problem with the ribbon is that discoverability is extremely slow. If I'm looking for a piece of functionality, it's much faster to read through text menus

The problem with the ribbon is that discoverability is extremely slow. If I'm looking for a piece of functionality, it's much faster to read through text menus looking for related words than to inspect a similar number of unfamiliar icons to figure out if they are related. Its keyboard usability is also not as consistent (e.g. alt+f, o to open a file from almost anywhere in the app) Once you know where everything is and what the icons mean, it's probably better than nested menus for use with the mouse. Since that describes most of the person-hours in the software, this is an improvement on average. New users and those who lean heavily on the keyboard still aren't going to like it, though.